1. Field of the Invention.
This invention relates to a new and improved vibration damper which is particularly, though not exclusively, adapted for use in the damping of wind generated or "aeolian" vibrations in power transmission cables or like suspended elongate members to prevent the self-destruction of the same and/or of the supporting structures therefor.
2. Description of the Prior Art.
Although vibration dampers for use in the damping of wind generated vibrations in suspended elongate members such as power transmission cables have long been known to take the form, for example, of the "Stockbridge" type damper disclosed in U.S. Pat. No. 1,992,538 of Feb. 26, 1935, it will be readily understood that a variety of not insignificant structural and functional shortcomings have come to light regarding this type of vibration damper. More specifically, since the support members which support the vibration absorbing or inertia weights in the "Stockbridge" type vibration dampers are non-rigid, taking, for example, the form of a seven-strand, braided galvanized cable with inherently poor vibration damping characteristics, it may be understood that the repeated function thereof in transferring vibrational energy to the vibration absorbing weights, and attendant "working" of the cable strands, can and does result in the need for relatively frequent replacement of the damper to forestall structural and/or functional failure of those members. Also, this repeated "working" of, and abrasion by and between these galvanized cable strands, can and does result in the removal of the zinc coating therefrom with attendant undesirable rusting and weakening of the cable strands. Too, since these support members are generally clamped directly to the connecting clamp, which is in turn clamped directly to the power transmission cable, the significant vibration absorbing advantages which are provided by the use of an intermediate vibration damping boundary member of proven vibration damping characteristics as, for example, butyl or neoprene rubber, are unnecessarily sacrificed. This direct, and particularly forceful, clamping of the support cable to the connecting clamp, and the particularly forceful, wedge-type of attachment of the support cable to the inertia weights, in the manufacture of a typical "Stockbridge" type vibration damper, can result in unacceptable damage to the support cable and/or connecting clamp during the damper manufacturing process with attendant increase in the overall cost of damper manufacture. Also, since this connecting clamp of the prior art is generally made of cast iron and is thus relatively heavy, the same adds unnecessarily to the undamped weight of the power transmission cable at the critical point of damper attachment. Further, since the vibration absorbing or inertia weights are generally symmetrically disposed on the "Stockbridge" type dampers, it may be understood that the frequency range through which these prior art dampers exhibit effectively high vibration resistance and real power consumption is unnecessarily limited. In addition, since the vibration absorbing or inertia weights are generally fixedly secured to the support members in the "Stockbridge" type dampers, it becomes difficult and inconvenient, if not, as a practical matter, impossible, to replace those weights with weights of other and different mass characteristics to adapt these prior art dampers to the effective damping of vibrations throughout different frequency ranges as oftentimes may become most desirable for varying vibration damper applications.